With the Hookshot, Link can reach Thieves' Town, hidden in the Village of Outcasts in the Dark World.
Get the Map
Go north and drop down from the ledge to the area below, but be careful to avoid the Zazak that is walking around. Go north and you will see a Spark spinning around a statue. The red Zazak nearby will try to spit fireballs at you. Go west from the Spark that is spinning around the statue, and open the chest to get the map.
Get the Compass
Go north from the Spark that is spinning around the statue until you reach the next area. You will see a chest on the upper level. It contains a red rupee. If you get it, drop back down to the lower level. Go to the easternmost side of the room, and keep going east to reach the next room.
Beware of the Rabbit Beams that are hiding under walkways in this room. A Rabbit Beam is a floating swarm of stars that will try to touch you. If it does, you are temporarily turned into a rabbit. You will not be able to attack or use items until the effect wears off or until you are hit by an enemy while in rabbit form. Rabbit Beams can be destroyed using any of the magic Medallions.
Go the southwest corner of this room, but stay north of the statue that has two Sparks spinning around it, because there is a Rabbit Beam hiding under the southern ledge. When it is safe to do so, go south via the southwest exit of the room.
Go south and up the stairs to reach the upper level. Go southwest to reach the chest. Open it to get the Compass.
Get the Big Key
Drop down to the lower level and quickly go west to the next room to avoid the Rabbit Beam.
Open the chest to get the Big Key.
Get a Key
Go east to the previous room and quickly go north to avoid the Rabbit Beam. Go north to the next room.
Go up the stairs to the upper level, and go to the north wall to find a locked door near the northeast corner. Go through. Kill or ignore the Stalfos and go to the northeast corner of the room. Pick up the northeast skull to find a key. Go to the southwest of the room and go through the locked door there.
Get a Second Key
Kill or ignore the Zazaks, and avoid the Winder that moves around the room, and go through the west door.
There are Gibos that float around the room. They can only be harmed by hitting the small core that sometimes floats out of the main body. There is also a Bubble floating around the room. You can use the Magic Powder on it to turn it into a Fairy. Get past these enemies and carefully go west across the conveyor belts, and go through the west door.
There is a large conveyor belt in this room, as well as some Gibos, a Bubble, and a Winder. Go north up the conveyor belt and go through the north door.
There are hidden Zols in the floor that will appear as you walk around, so watch out for them. Pick up the skull to get a key.
Bomb the Floor
Place a bomb near the crystal switch, then go to the north side of the room and wait for it to detonate. The crystal switch should now be blue, so the blue blocks are lowered. Go north through the locked door.
Kill or ignore the Buzz that crawls around this room. The Hookshot kills it in one hit. Ignore the lever in the wall; it's a trap that causes Skullropes to fall from above. Instead, pick up the southeast skull to reveal a switch. Step on it to open the east door. Go through it.
Go east, killing or ignoring the Buzzes, until you reach a room with a single window that is shining light onto the middle of the floor. Kill or ignore the Buzzes, and ignore the chest and skulls in this room for the moment. Throw a bomb onto the cracked floor that the light is shining on (you can press A to pick up a bomb after you place it, and press A to throw it after you have picked it up). When you successfully open a hole in the floor where the light is shining, open the chest and pick up the skulls to get some bombs.
Get a Third Key
Make your way back to the room with the crystal switch. Hit the switch with the Boomerang or Hookshot, then go south to stand next to the crystal switch. Place a bomb near the crystal switch and go to the south side of the room. Make sure that the crystal switch turns blue and the blue blocks are lowered, then go through the south exit.
Go through the northeast door. (If it's blocked by a blue block, go north and use a bomb on the crystal switch to turn it blue, then go south and go through the northeast door.)
Go east, killing or ignoring the Gibo and the two red Zazaks, and go through the east door.
This room has many conveyor belts, Zazaks, spike Traps, and a Stalfos. Go down the stairs in the north wall.
Kill or ignore the two Zazaks and the Stalfos. Lift the large block and go south through the door.
Kill or ignore the lone Zazak and go through the east door.
There are hidden Zols in this room, as well as a number of Zazaks. There is also a Rabbit Beam hidden under the northwest skull. Open the jail cell doors and talk to the maiden. Open the chest in her jail cell to get a key.
Get the Titan's Mitt
Leave the jail the way that you came in, and go through the west door to reach a room with a conveyor belt in the middle. Go through the locked southwest door.
In a few moments the floor around the big chest will crumble, so use the Hammer on a Mole and open the big chest to get the Titan's Mitt. (If you didn't make it in time, use the Hookshot on one of the northernmost moles to reach the corner of the platform with the big chest.) The Titan's Mitt allows you to lift black rocks, boulders, and skulls, in addition to white ones.
Reach the Dungeon Boss
If the tiles around the big chest have all fallen away, use the Hammer on the southeast or southwest Mole, then use the Hookshot on the statue across the gap, but be sure to walk toward the statue to avoid slipping off of the edge behind you. Then go through the door.
Go past the conveyor belt and go through the southeast door, then go through the north door. Lift the large block and throw it, then go up the stairs in the north wall.
Lift the northeast skull to reveal a floor switch. Step on it to open the east door. Go through it.
Go through the north door and you will reach the room where the light is shining through the hole that you bombed in the room above. Go north until the door closes behind you. Go to the south side of the room.
Blind the Thief
At first, Blind moves side to side at the top of the room, and will occasionally stop and shoot a laser from its eyes in the direction that it is looking.
Eventually, Blind moves to the south side of the room. At this point, you can hit Blind's head while avoiding the laser beams. Whenever you hit Blind's head, it will spit orbs in many directions for a while. Be careful to dodge these.
After you hit Blind's head three times, it will separate from its body and start floating around the room, spitting an orb from time to time. A new head will replace the one that separated from Blind's body.
Repeat the process of hitting the head on Blind's body, and after you hit it enough times, it will also start floating around the room.
Resume your attacks on the body's head while dodging the many orbs and laser beams. If needed, you can use the Magic Cape to avoid the attacks for a short time. After you kill the third head, Blind is defeated.
Take the Heart Container and the crystal. There will be a cutscene. Your health and magic will be refilled and you will be sent back outside.
Now that you have the Titan's Mitt, there are many helpful upgrades that you can get now.